In a method known as conventional color photography, a color photosensitive material for photographing use (the so-called color negative) generally comprises a layer capable of recording blue light to form a yellow image, a layer capable of recording green light to form a magenta image and a layer capable of recording red light to form a cyan image. When such a material undergoes development-processing after exposure, the silver halide grains having latent images formed by the exposure are reduced to silver, while the developing agent is oxidized. The oxidized developing agent reacts with dye-providing couplers (that is, undergoes coupling reaction) to form dye images. From the resultant material, the undeveloped silver halide and the developed silver are removed in a bleach-fix step subsequent to the development step. The negative dye images thus obtained are projected onto a color photosensitive material for printing use, and the thus exposed printing material is subjected to development and bleach-fix steps similar to the above, thereby obtaining a color print.
The so-called color negative photosensitive material further contains colloidal silver and dyes having a filtering function for imparting spectral sensitivity differences to the three kinds of sensitive layers, and fine-grain silver or dyes for the anti-halation purpose. Of these additives, the metal silver, such as colloidal silver, is removed in a bleaching step.
Also, another method of forming color images in a reprinting material is known, wherein the image information present in a color negative as described above is read by a photoelectric means, subjected to image processing to be converted into image information for recording, and then recorded in a printing material.
In particular, the development of digital photoprinters has been advanced as an embodiment of the foregoing method. An example of such photoprinters is described in JP-A-7-015593 (The term "JP-A" as used herein means an "unexamined published Japanese patent application") In a digital photoprinter, the image information of a color negative is converted into digital signals, and recording light modulated in accordance with those digital signals is used for scanning exposure of photosensitive materials, such as color paper, to provide finished prints.
The methods cited above presuppose usual development, bleach and fixation steps, and so their processing steps are complex.
In the conversion of image information into digital signals, however, the image information as original is not required in principle to be dye images. For instance, EP 526,931 describes the method in which a multilayer photosensitive material constituted of a layer forming a silver image alone and a layer forming both silver and dye images is exposed and then developed, and the thus obtained image information is read. Further, JP-A-6-266066 describes the method in which all the three layers constituting a multilayer photosensitive material are free from dyes, and the information as to residual silver halide and developed silver is read.
Although the above-cited methods simplify photographic processing, they presuppose digitized image processing. Therefore, in contrast to conventional dye images, the images obtained by those methods cannot be used for the exposure by direct projection onto color paper and the like. Even when the digital processing is performed, however, the developed silver and the silver halide are lower in concentration than dyes. Thus, a smaller amount of information is derived therefrom; as a result, the image quality is lowered. In addition, as usual color couplers are used as coloring material, colors are gradually developed in the Dmin area unless any processing is given to the couplers after development. Therefore, a certain processing for fixation or stopping the development is carried out.
As other coloring materials used in a method of forming images, there are known nondiffusible compounds of the kind which release diffusible dyes responding positively or negatively to silver development. For instance, such compounds are described, e.g., in EP-A2-0220746, U.S. Pat. No. 4,783,396, Kokai Giho 87-6199, JP-A-64-13546, U.S. Pat. No. 4,500,626 and U.S. Pat. No. 4,639,408. Those compounds are mainly used for transferring diffusible dyes into an image-receiving material to form a print.
On the other hand, as a processing method of a photosensitive material using a silver halide, a simple rapid process using a heat development has been developed and as the examples, goods such as Dry silver (trade mark) by Minnesota Mining and Manufacturing Company, PICTROGRAPHY (trade mark) by Fuji Photo Film Co., Ltd, and PICTROSTAT (trade name) by Fuji Photo Film Co., Ltd., have been known. However, they are black and white or color printing materials and photosensitive materials for photographing use by a conventional heat development have not been known.
Also, as a form of heat development, a process of heat-developing in the presence of a small amount of water and a base and/or a base precursor is known, for example, an example of the process is described in JP-B-2-51494 (the term "JP-B" as used herein means an "examined Japanese patent publication"). However, the image-forming method described in the above patent is a process that dye-providing substances, which are reductive to a light-sensitive silver halide and release hydrophilic dyes by causing a reaction when heated together with a light-sensitive silver halide, are used, the dyes released at the heat-development is transferred onto an image-receiving material, and the image-receiving material having thus transferred dyes is used as a color print.
As mentioned above, conventional methods for color photographic processing are complex, and so more simplified methods are desired to be developed. Further, disposal of processing solutions used in bleaching and fixing steps is required. The methods described in EP 526,931 and JP-A-6-266066, though they are simplified, presuppose digitalized image processing, and so the images obtained thereby cannot be used for the exposure performed by direct projection onto color paper or the like.